An operating system may view a processor as a logical processor or logical processing unit. The logical processor is backed by a certain socket or physical processor. The physical assignment of processors is typically determined when a machine is powered and initialized, before the operating system is loaded. Normally, once the assignment of logical-to-physical processors is made, the assignment is not modified.
However, under certain stringent conditions, the assignment of logical-to-physical processors can be modified. In particular, if a physical processor fails, the assignment can be modified, assuming a spare processor exists within the processing environment. Specifically, in situations of a failed physical processor, the assignment may be modified, such that the spare processor, instead of the failed processor, backs the logical processor(s).